My take on this (articulated fairly recently, actually) is that you should take the fall whenever you feel like it. That is, if you have to, you should take the fall. If it seems like the more interesting thing to do, you should take the fall. If you think you are likely to learn something by taking the fall, you should take the fall.

On the other hand, if you don't feel a need, or you think you are more likely to learn something by avoiding the fall, then go ahead and avoid it.

Staying responsible to yourself for your own learning seems like the quickest way to learn.